An apparatus that uses an X-ray CT (Computed Tomography) system to scan test objects and processes the accumulated data with a computer, thereby imaging the inside of the test object.
Specifically, the X-ray CT system exposes X-rays onto the test object from different angles multiple times, extracts the X-rays penetrating the test object to an X-ray detector, and accumulates multiple detection data. The accumulated detection data is A/D-converted in a data accumulating unit, then sent to a console apparatus. The console apparatus carries out pretreatment, etc. on the detected data and produces projected data. Then, the console apparatus carries out reconstruction processing based on the projected data and produces volume data based on tomographic image data or a plurality of tomographic image data. The volume data is data set expressing a 3-dimensional distribution of a CT number corresponding to a 3-dimensional region of the test object.
Moreover, the X-ray CT system includes an apparatus such as a multi-slice X-ray CT system that can carry out high-definition (high resolution) imaging over a wide range per unit time. This multi-slice X-ray CT system uses detector elements in m column in an anteroposterior direction and the n rows in the direction orthogonally intersecting the anteroposterior direction as the detector used in the single slice X-ray CT system, that is, a two-dimensional detector of a configuration with the m columns and n rows arranged.
Due to such a multi-slice X-ray CT system, the larger a detector is (the greater the number of detector elements configuring the detector), the greater the possibility of acquiring projection data over a wider region in a single image. In other words, by temporarily imaging using a multi-slice X-ray CT system provided with such a detector, it is possible to generate volume data for a specific site at a high frame rate (hereinafter, sometimes referred to as a “Dynamic Volume scan”). This makes it possible to assess the movement of the specific region within a unit of time by means of 3-dimensional images.
Moreover, a medical image processing apparatus exists that reconstructs volume data based on the projected data obtained from the X-ray CT system and generated medical images from the volume data.
Meanwhile, when flexible sites configured by a plurality of parts such as joints, etc. are subjected to observation and the movements thereof are evaluated, there is a demand for displaying small movements, allowing for observation, by increasing the frame rate when each part of the observation subject attains the positional relation determined by an operator. Specifically, for example, when there is a reaction from a patient when the joints of the arm are bent by the patient (for example, a reaction of the patient such as “it hurts”), there is a desire to allow a close investigation into the condition of the bone before and after the reaction.
Moreover, the speed of movements of the observation subject such as the joints, etc. are not always constant, and when a series of movements are displayed at the same frame rate, the detailed movement of the observation subject may be difficult to observe regarding the timing points at which the observation subject rapidly moves. Accordingly, there is a desire to allow observation of detailed movements by increasing the frame rate as the observation subject rapidly moves. Moreover, at this time, for example, there is a desire for displaying the observation subject at a higher resolution in order to allow observation of more detailed movements. Furthermore, the frame rate and resolution are determined by reconstruction conditions. Moreover, when the frame rate or the resolution is increased, the processing load related to reconstruction increases, thereby prolonging the processing time. Accordingly, the reconstruction conditions are determined in advance in correspondence with the time required to generate the medical images and required image quality.
In this manner, there are cases when there is a desire for displaying, allowing for observation of detailed movements of the observation subject, by changing the reconstruction conditions in correspondence with the positional relation based on absolute positions such as “the positional relation determined in advance”, etc. and relative positional relation of the observation subject between each timing point such as “speed of movement of the observation subject”, etc. Furthermore, the frame rate of the displayed image is determined based on the frame rate of the acquired volume data (that is, the volume rate). Furthermore, hereinafter, the volume data may be referred to as “image data”.